Need help for Pure Sine Wave Inverter

[MAXPAYNE]

After some study I hv decided to design a 1000 Watt pure sine wave inverter. I need advice from the Power Electronics Experts (LOL!) in this forum for the following issues.... Smiley

1) I have chosen to use 12V DC >>> PUSH-PULL>>> 400V DC >>> SWITCHING H-BRIDGE>>> 220V AC WITH HARMONICS >>> FILTERING >>> 220V AC PURE SINE WAVE ( pls advice if it is correct or not or any other better idea)

2) pls advice the switching frequency both in DC-DC and DC-AC stage.

3) What should I chose in both stage? IGBT or MOSFET ? I m finding hard-one to chose any of them

4) Should I use FULL BRIDGE topology in DC-DC stage instead of PUSH-PULL ?

5) I want to use gate driver IC for driving 4 MOSFET/IGBT in (400V DC >>> SWITCHING H-BRIDGE>>> 220V AC WITH HARMONICS ) ? pls suggest which IC should I use ..

6) Any other concept for designing pure sine wave inverter instead of (12V DC >>> PUSH-PULL>>> 400V DC >>> SWITCHING H-BRIDGE>>> 220V AC WITH HARMONICS>>> FILTERING >>> 220V AC PURE SINE WAVE)

w8ing for your ans guys ......

 

[kabiru]

Hello Max,you can used DC-DC converter with swiching freq from 38-40khz,then you can use your pic to generate your pwm signal.

 

[MAXPAYNE]

Hello Max,you can used DC-DC converter with swiching freq from 38-40khz,then you can use your pic to generate your pwm signal.

Thanks for your answer. Can u elaborate more for section 1 to 6 in my post. :|

 

[kabiru]

1,i suggest you should used push pull dc-dc converter. 2.for Dc-DC converter 38khz-40khz and for your 50Hz use pic to generate your pwm. 3.you can use mosfet for it. 4.you can use push pull to reduce component been used. 5.you can use IR2110. 6.the most important thing is to generate your spwm the use your driver to switch it through your step up transformer if you are using low freq iron core,but if you don't want that topology then you can use your dc-dc converter and your low pass filter to eliminate your harmonics.

 

[goldsmith]

Hi Dear All
There are more better ways to obtain your aim .
Such as SPWM method and link inverter ! You can increase your amplitude by a simple DC/DC converter e.g push pull or H bridge ( h bridge is better ) and with HF transformer and without any feed back . and after that and H bridge with SPWM and without Any transformer simply .
Best Wishes
Goldsmith

 

[MAXPAYNE]

Can u elaborate more the two methods, SPWM method and link inverter ? Why DC-DC converter will not include any feed back??? Then how can it be constant 400V DC with change of load ?

 

[goldsmith]

Can u elaborate more the two methods, SPWM method and link inverter ? Why DC-DC converter will not include any feed back??? Then how can it be constant 400V DC with change of load ?

Hi again
Both are the same .

and about feed back , you'll not need it , for simple loads , but if your load is unknown , because of out put filter that is at butter worth family , if your load become higher than normalized impedance the out put wave of last stage will go to the higher amplitudes , and you should take a DC feed back from out put to your first stage .
Best Wishes
Goldsmith

 

[MAXPAYNE]

Hi again
Both are the same .

and about feed back , you'll not need it , for simple loads , but if your load is unknown , because of out put filter that is at butter worth family , if your load become higher than normalized impedance the out put wave of last stage will go to the higher amplitudes , and you should take a DC feed back from out put to your first stage .
Best Wishes
Goldsmith

Obviously the load will be unknown. and it will vary from 200W to 1000W and may be inductive in nature. But I m confused about from where I should take feedback. Form 400V DC output or from 220V AC output ???

 

[goldsmith]

Hi again
It is simple .
you will take feed back from out put AC voltage ! do you know how ? again simply . you'll take a divided voltage ( AC ) with two simple resistor and then you'll rectify it and it will be the DC feed back of your first stage . and you can use a driver IC for first stage .
e.g : an SG3526N
Best Wishes
Goldsmith

 

[MAXPAYNE]

I m really grateful to you for such a nice reply. One more question is circling around my mind. What if I take feedback from the 400V DC to SG3525?

 

[goldsmith]

simple ! if you take feed back from that , you can sense increasing the voltage ! it will happen after your LPF.
Best Wishes
Goldsmith

 

[MAXPAYNE]

I couldn;t understand .

What will be correct ? taking feedback from 220V AC output or from 400V DC output ? Also please elaborate ..

 

[goldsmith]

Sorry because of not clear reply .
No problem
Taking feed back from AC out put ( you'll rectify your feed back voltage and filter it ) and affect it on first stage controller .

 

[Tahmid]

After some study I hv decided to design a 1000 Watt pure sine wave inverter. I need advice from the Power Electronics Experts (LOL!) in this forum for the following issues.... Smiley

1) I have chosen to use 12V DC >>> PUSH-PULL>>> 400V DC >>> SWITCHING H-BRIDGE>>> 220V AC WITH HARMONICS >>> FILTERING >>> 220V AC PURE SINE WAVE ( pls advice if it is correct or not or any other better idea)

2) pls advice the switching frequency both in DC-DC and DC-AC stage.

3) What should I chose in both stage? IGBT or MOSFET ? I m finding hard-one to chose any of them

4) Should I use FULL BRIDGE topology in DC-DC stage instead of PUSH-PULL ?

5) I want to use gate driver IC for driving 4 MOSFET/IGBT in (400V DC >>> SWITCHING H-BRIDGE>>> 220V AC WITH HARMONICS ) ? pls suggest which IC should I use ..

6) Any other concept for designing pure sine wave inverter instead of (12V DC >>> PUSH-PULL>>> 400V DC >>> SWITCHING H-BRIDGE>>> 220V AC WITH HARMONICS>>> FILTERING >>> 220V AC PURE SINE WAVE)

w8ing for your ans guys ......

1) That is the basic concept. You can see a more detailed block diagram here:


For the first part, you can use SG3525 operating at 30kHz to 70kHz. You can use push-pull but at 1kW, it might be better to use a full-bridge converter. For that, you'd need high-low side drivers (isolated/bootstrapped gate drive). At 1kW load, assuming an efficiency of 80%, the max current draw (when battery voltage falls to 11V under load) is about 114A. For 1kW inverter, you should use 48V and the current will then be about 29A when battery is around 44V. Or at least you can use 24V battery.

For a sine wave inverter, the 2nd part - the 400VDC to 220VAC will be controlled by the microcontroller. You can use IGBT or MOSFET. For 1kW, you can use MOSFET. By using MOSFETs in the H-bridge in the 2nd part, you can use higher frequency such as 50kHz modulation frequency. Thus, you will need smaller inductor and capacitor for filtering. If you use IGBT, you have to use lower frequency such as 16kHz unless you use some of the more expensive IGBTs that can handle higher frequencies. These IGBTs are not available in Bangladesh. MOSFETs will work quite well and you can use MOSFETs with low RDS(on) and/or parallel multiple MOSFETs to reduce power loss.

2) For DC-DC for 12V to 400V, you can use around 50kHz. Adjust this depending on parameters such as switching loss, driving current, transformer and components size, value, etc. But 50kHz should be a good frequency. For DC-AC for 400VDC to 220VAC, you can use modulation frequency 16kHz, 32kHz, 48kHz, 64kHz, etc. If you're using MOSFETs, you can use 48kHz or 64kHz to minimize size of inductor, capacitor, etc

3) For 1kW, I would recommend MOSFETs as you can use higher frequency and use smaller parts.

4) For 1kW, I think it's better to use full bridge than push pull.

5) You need to use high-low side drivers. You can use IR2110, IR2113, etc which are available in Bangladesh. Beware of fake parts which seem to be abundant here.

6) For feedback, instead of using feedback in the 2nd stage with the microcontroller, you might want to use feedback in the 1st stage using the SG3525 as the circuit is relatively simple. The PIC will have problems maintaining feedback if it has to do loads of stuff, especially if it's going to be generating SPWM with 64kHz frequency. This applies to PIC16 and PIC18 due to the small time available after SPWM at 64kHz. For this task, the PIC16 and PIC18 are too slow. So, you can just use the SG3525 for feedback to maintain a constant DC bus voltage. Or the DC bus voltage may be varied by the SG3525 by sensing output AC voltage to maintain constant output. Sensing from AC output would result in more accurate feedback and output voltage.

Hope this helps.
Tahmid.

 

[MAXPAYNE]

Tahmid,

U simply answered all my questions. I m really gr8ful to you for putting everything such a nice way. I m a bit busy with my studies and job at the moment. When I will start design I will consult with u I guess u r frm Uttara like me. Hope u will never mind meeting one day.

please suggest some MOSFETs for both the stages DC-DC and DC-AC as u r very much experienced ... and how can I identify fake parts ???

 

[goldsmith]

please suggest some MOSFETs for both the stages DC-DC and DC-AC as u r very much experienced ... and how can I identify fake parts ???

selecting mosfets , is instead of your frequency .
But i can suggest you some types : e.g : IRFP450 or IRFP450LC IRFP460 IRFP460 LC
Food luck
Goldsmith

 

[Tahmid]

For the DC-DC stage, you can parallel multiple IRF3205s. Each has a high current rating and low RDS(on), so paralleling will increase current capacity and decrease RDS(on) further.

For the DC-AC stage, you can use IRFP460s.

Of course, you can choose from thousands and thousands of MOSFETs. But I've selected IRF3205 and IRFP460 as they are widely available in our market and the price is rather reasonable.

For IR2110 and IR2113, I don't know how you can detect fakes. All the ones I've used created many problems. But as far as I know and have been told, most of the IR2110s that come to our market are fake.

Hope this helps.
Tahmid.

 

[MAXPAYNE]

If I chose the modulation frequency 64 Khz , will IRFP460 be suitable considering the gate charge ?

 

[Tahmid]

You can use IRFP460, but you will need to drive the gate with higher current. If you use a high-low side driver (like the IR2110 mentioned), this won't be a problem.

 

[goldsmith]

For the DC-DC stage, you can parallel multiple IRF3205s. Each has a high current rating and low RDS(on), so paralleling will increase current capacity and decrease RDS(on) further.

Dear Tahmid
Hi
I don't think it is good way , because there are many suitable mosfets available and the disadvantage of this way is , the ciss naturally will increase and the inrush current for drive will increase too .
Regards
Goldsmith